• 대한화학회지
• /
• 제32권3호
• /
• pp.243-248
• /
• 1988

수용액에서 몇가지 란탄 착화합물의 hypersensitive 전이대를 연구하였다. 리간드의 염기도$(pK_a)$와 란탄 착화합물의 hypersensitive 전이대의 진동자 세기 사이에 정립된 선형 관계에 근거를 두고, 금속-리간드 결합간에 존재하는 공유 결합성을 anthranilate, pyrazine-2-carboxylate, 및 pyruvate 착화합물에 대해서 논하였다.

• Macromolecular Research
• /
• 제8권4호
• /
• pp.147-152
• /
• 2000

The activity of periodic acid as an initiator for the polymerization of acrylamide in aqueous medium was investigated. The rate of polymerization was found to be proportional to the monomer concentration to the 1.5th power in the range of 1.41-5.64 mol/L. The reaction order to the periodic acid concentration was 0.49, which indicated a bimolecular mechanism for the termination reaction in the range of 0.5-4.0$\times$10$\^$-2/ mol/L. Propagation rate increased with raising the temperature according to an Arrhenius expression resulting in the exhibition of an apparent activation energy of 87.8 kJ/mol in the temperature range of 60-80$\^{C}$. The addition of hydroquinone as a radical scavenger stopped the polymerization of acrylamide initiated by periodic acid. These results support that the polymerization proceeds via a radical chain mechanism .

• Bulletin of the Korean Chemical Society
• /
• 제1권3호
• /
• pp.78-82
• /
• 1980

Solutions of $Cd^{2+}$, $Co^{2+}$ and $Ni^{2+}$ were mixed with the solutions of hydroxycarboxylic acids such as salicylic, lactic and mandelic acids in the presence of cation exchange resin at room temperature. The distribution ratios of the metal ions between resin and solution were measured, using radioactive metal ions as tracer. From the observed variation of the distribution ratios with the acid anion concentrations, it was concluded that $Cd^{2+}$, $Co^{2+}$ and $Ni^{2+}$ formed the one-to-one complexes with salicylate, lactate and mandelate ions in aqueous, 20 % ethanol-water and 20 % acetone-water solutions. The results of the present study indicated that the relative stabilities of the metal-acid complexes in solution increased in the order: $Cd^{2+}$ <$Co^{2+}$ <$Ni^{2+}$ complexes. Salicylate

• Bulletin of the Korean Chemical Society
• /
• 제14권1호
• /
• pp.34-34
• /
• 1993

The gelation phenomena of N-methylolated PAAm (M-PAAm) in aqueous media was studied. The critical gelation concentration (CGC) was very close to the calculated $C^*$ of the scaling theory. But the CGC of lower MW M-PAAm deviated from $C^*$ due to contamination of small molecules. We propose that the CGC is the close packing configuration of polymer molecules in solution. The experimental results of the gelation of M-PAAm/PAAm mixture proved that the close packing configuration is essential to make a gel. We calculated the minimum quantity of M-PAAm to make M-PAAm/PAAm mixture a gel by using the close packing configuration. We used a lattice model.

• Bulletin of the Korean Chemical Society
• /
• 제11권2호
• /
• pp.144-149
• /
• 1990

Conformational free energy calculations using an empirical potential function (ECEPP/2) and the hydration shell model were carried out on the sulfonylurea herbicides of bensulfuron methyl (Londax) and metsulfuron methyl (Ally). The conformational energy was minimized from starting conformations which included possible combinations of torsion angles in the molecule. The conformational entropy of each conformation was computed using a harmonic approximation. To understand the hydration effect on the conformation of the molecule in aqueous solution, the hydration free energy of each group was calculated and compared each other. It was found that the low-free-energy conformations of two molecules in aqueous solution prefer the overall folded structure, in which an interaction between the carbonyl group of ester in aryl ring and the first amido group of urea bridge plays an important role. From the analysis of total free energy, the hydration and conformational entropy are known to be essential in stabilizing low-free-energy conformations of Londax, whereas the conformational energy is proved to be a major contribution to the total free energy of low-free-energy conformations of Ally.

• Bulletin of the Korean Chemical Society
• /
• 제12권6호
• /
• pp.629-632
• /
• 1991

The rate constants for the formation and dissociation of nickel(II) and cobalt(II) complexes with mandelate have been determined by the pressure-jump relaxation study. The forward and reverse rate constants for the mandelate complex formation reactions were obtained to be $k_f=3.60{\times}10^4\;M^{-1}s^{-1}$ and $k_r=1.73{\times}10^2\;s^{-1}$ for the nickel(II), and $k_f=1.75{\times}10^5\;M^{-1}s{-1}$ and $2.33{\times}10^3\;s^{-1}$ for the cobalt(II) in aqueous solution of zero ionic strength ($(\mu{\to}0)\;at\;25^{\circ}C$. The results were interpreted by the use of the multistep complex formation mechanism. The rate constants evaluated for each individual steps in the multistep mechanism draw a conclusion that the rate of the reaction would be controlled by the chelate ring closure step in concert with the solvent exchange step in the nickel(II) complexation, while solely by the chelate ring closure step for the cobalt(II) complex.

• Bulletin of the Korean Chemical Society
• /
• 제8권4호
• /
• pp.261-264
• /
• 1987

Benoxaprofen (2-(4-chlorophenyl)-${\alpha}$ -methyl-5-benzoxazole acetic acid) is a nonsteroidal anti-inflammatory drug that causes acute cutaneous phototoxicity. The ability of benoxaprofen (BXP) and its photoproduct, decarboxybenoxaprofen (DBXP) to photosensitize the decomposition of tryptophan was evaluated in various media such as water, ethanol and aqueous micellar dispersions of surfactants. The weak photosensitization of BXP in water was found to be enhanced in cationic CTAB micelle system, but yielded little difference in anionic SDS micelles. In ethanol solution, BXP was determined to photosensitize the decomposition of tryptophan, but no photosensitization was observed with DBXP. All of these results implicate that the anion radical of BXP may play a major role in the photosensitization in hydrophobic micellar phase, forming superoxide through interaction with oxygen as demonstrated by observation that the photosensitization was inhibited by superoxide dismutase.

• Bulletin of the Korean Chemical Society
• /
• 제8권5호
• /
• pp.362-366
• /
• 1987

Modification of n-Si electrodes coated by photogalvanostatically with polyaniline and polypyrrole in aqueous solutions considerably enhanced the stability and the spectral response of the photoelectrodes. A polypyrrole coated electrode incorporated with redox couple $Fe(CN)_{6}^{3-_6}$ / $Fe(CN)_{6}^{4-_6}$ yielded a photocurrent density of 400${\mu}A/cm^2$ for about 120 hours. Broad spectral responses over 300-850 nm were observed for both polymer coated electrodes of which polypyrrole coated one showed better current conversion efficiency.

• Archives of Pharmacal Research
• /
• 제2권2호
• /
• pp.111-114
• /
• 1979

Diazepam was investigated in aqueous buffer media using pulsed rotation voltammetry. The dependence of half-wave potentials on pH indicated a two proton involvement in a two electron transfer reduction in the pH range 3-10. Dizaepam at micromolar concentration levels may be determined by measurement of the limiting difference current.

• Bulletin of the Korean Chemical Society
• /
• 제33권11호
• /
• pp.3593-3596
• /
• 2012

The water-soluble conjugated polymer with fluorescence quenching as a result of electrostatic interaction and aggregation was synthesized through Suzuki polymerization. The absorption and emission of anionic polymer (a-PFP) is blue shifted as compared with cationic polymer (c-PFP) although getting same backbone, and the absolute PL quantum efficiency of a-PFP in water is over 90% due to good solubility in aqueous solution. We anticipate that the fluorescence quenching of anionic and cationic polymers, with same conjugated backbone, could be shown in aqueous solution.